exotherms had sprayed across the ground; the sub had burned tons of fuel in melting its way to the surface. The rest of the mission must be powered by just the exotherms they could carry and what fuels they could find beneath the snow.
More than anything else, the exotherms were the trick that made this walk in the Dark possible. Before the invention of the microscope, the “great thinkers” claimed that what separated the higher animals from the rest of life was their ability to survive as individuals through the Great Dark. Plants and simpler animals died; it was only their encysted eggs that survived. Nowadays, it was known that many single-celled animals survived freezing just fine, and without having to retreat to deepnesses. Even stranger, and this had been discovered by biologists at Kingschool while Sherkaner was an undergraduate, there were forms of Lesser Bacteria that lived in volcanoes and stayed active right through the Dark. Sherkaner had been very taken by these microscopic creatures. The professors assumed that such creatures must suspend or sporulate when a volcano went cold, but he wondered if there might be varieties that could live through freezes by making their own heat. After all, even in the Dark, there was still plenty of oxygen—and in most places there was a layer of organic ruin beneath the airsnow. If there were some catalyst for starting oxidation at super-low temperatures, maybe the little bugs could just “burn” vegetation between volcanic surges. Such bacteria would be the best adapted of all to live after Dark.
In retrospect, it was mainly Sherkaner’s ignorance that permitted him to entertain the idea. The two life strategies required entirely different chemistries. The external oxidation effect was very weak, and in warm environments nonexistent. In many situations, the trick was a serious disability to the little bugs; the two metabolisms were generally poisonous to each other. In the Dark, they would gain a very slight advantage if they were near a periodic volcanic hot spot. It would never have been noticed if Sherkaner hadn’t gone looking for it. He had turned an undergraduate biology lab into a frozen swamp and gotten himself (temporarily) kicked out of school, but there they were: his exotherms.
After seven years of selective breeding by the Materials Research Department, the bacteria had a pure, high-velocity oxidizing metabolism. So when Sherkaner slopped exotherm sludge into the airsnow, there was a burst of vapor, and then a tiny glow that faded as the still-liquid droplet sank and cooled. A second would pass and if you looked very carefully (and if the exotherms in that droplet had been lucky) you would see a faint light from beneath the snow, feeding across the surface of whatever buried organics there might be.
The glow was sprouting brighter now on his left. The airsnow shivered and slumped and some kind of steam curled out of it. Sherkaner tugged on the cable to Unnerby, guiding the team toward denser fuel. However clever the idea, using exotherms was still a form of firemaking. Airsnow was everywhere, but the combustibles were hidden. It was only the work of trillions of Lesser Bacteria that made it possible to find and use the fuel. For a while, even Materials Research had been intimidated by their creation. Like the mat algae on the Southern Banks, these tiny creatures were in a sense social. They moved and reproduced as fast as any mat that crawled the Banks. What if this excursion set the world on fire? But in fact the high-velocity metabolism was bacterial suicide. Underhill and company had at most fifteen hours before the last of their exotherms would all die.
Soon they were off the lake, and walking across a level field that had been the Base Commander’s bowling green in the Waning Years. Fuel was plentiful here; at one point the exotherms got into a fallen mound of vegetation, the remains of a traumtree. The pile glowed more and more warmly, until a brilliant emerald light exploded through the snow. For a few moments, the field and the buildings beyond were clearly visible. Then the green light faded, and there was just the heat-red glow.
They had come perhaps one hundred yards from the sub. If there were no obstacles, they had more than four thousand yards to go. The team settled into a painful routine: walk a few dozen yards, stop and spread exotherms. While Nizhnimor and Haven rested, Unnerby and Underhill would look about for where the exotherms had found the richest fuel. From those spots, they would top off everyone’s sludge panniers. Sometimes, there wasn’t much fuel to be found (walking across a wide cement slab), and about all they had to shovel was airsnow. They needed that, too; they needed to breathe. But without fuel for the exotherms, the cold quickly became numbing, spreading in from the joints in the suits and up from their footpads. Then success depended on Sherkaner successfully guessing where to go next.
Actually, Sherkaner found that pretty easy. He’d gotten his bearings by the light of the burning tree, and by now the patterns of airsnow that concealed vegetation were obvious. Things were okay; he wasn’t refreezing. The pain at the tips of his hands and feet was sharp, and every joint seemed to be a ring of fire, the pain of pressure- swelling, cold, and suit-chafe. Interesting problem, pain. So helpful, so obnoxious. Even the likes of Hrunkner Unnerby couldn’t entirely ignore it; he could hear Unnerby’s hoarse breath over the cable.
Stop, refill the panniers, top off the air, and then on again. Over and over. Gil Haven’s frostbite seemed to be getting worse. They stopped, tried to rearrange the cobber’s suit. Unnerby swapped places with Haven, to help Nizhnimor with the sled. “No problem, it’s only the midhands,” said Gil. But his labored breathing sounded much worse than Unnerby’s.
Even so, they were still doing better than Sherk had expected. They trudged on through the Dark, and their routine soon became almost automatic. All that was left was the pain… and the wonder. Sherkaner looked out through the tiny portholes of his helmet. Beyond the swirl of mist and the exotherms’ glow… there were gentle hills. It was not totally dark. Sometimes when his head was angled just right, he caught a glimpse of a reddish disk low in the western sky. He was seeing the sun of the Deepest Dark.
And through the tiny roof porthole, Sherkaner could see the stars.Weare here at last. The first to ever look upon the Deepest Dark. It was a world that some ancient philosophers had denied existence—for how can somethingbe, that can never be observed? But now it was seen. It did exist, centuries of cold and stillness… and stars everywhere. Even through the heavy glass of the porthole, even with only his topside eyes, he could see colors there that had never been seen in the stars before. If he would just stop for a while and angle all his eyes to watch, what more might he see? Most theorists figured the auroral patches would be gone without sunlight to drive them; others thought the aurora was somehow powered by the volcanoes that lived beneath them. There might be other lights here besides the stars….
A jerk on the cable brought him back to earth. “Keep moving, gotta keep moving.” Gil’s voice was gasping. No doubt he was relaying from Unnerby. Underhill started to apologize, then realized that it was Amberdon Nizhnimor, back by the sled, who had paused.
“What is it?” Sherkaner asked.
“…Amber saw… light in the east…. Keep moving.”
East. To the right. The glass on that side of his helmet was fogged. He had a vague impression of a near ridgeline. Their operation was within four miles of the coast. Over that ridge they’d have a clear view of the horizon. Either the light was quite close or very far away. Yes! There was a light, a pale glow that spread sideways and up. Aurora? Sherkaner clamped down on his curiosity, kept putting one foot in front of another. But God below, how he wished he could climb that ridge and look across the frozen sea!
Sherkaner was a good little trouper right up to the next sludge stop. He was shoveling a glowing mix of exotherms, fuel, and airsnow into Haven’s panniers when it happened. Five tiny lights raced into the western sky, leaving little corners here and there like some kind of slow lightning. One of the five faded to nothing, but the others drew quickly together and—lightblazed, so bright that Underhill’s upward vision blurred in pain. But out to the sides, he could still see. The brightness grew and grew, a thousand times brighter than the faded disk of the sun. Multiple shadows showed stark around them. Still brighter and brighter grew the four lights, till Sherkaner could feel the heat soaking through the shell-cover of his suit. The airsnow all across the field burst upward in misty white-out brilliance. The warmth increased a moment more, almost scalding now—and then faded, leaving his back with the warm feeling you have when you walk into the shade on a Middle Years summer day.
The mists swirled around them, making the first perceptible wind they had experienced since leaving the sub. Suddenly it was very cold, the mists sucking warmth from their suits; only their boots were designed for immersion. The light was fading now, the air and water cooling to crystal and falling back to earth. Underhill risked focusing his upward eyes: The fierce points of light had spread into glowing disks, fading even as he watched. Where they overlapped, he saw a wavering and a folding, aurora-like; so they were localized in range as well as angle. Four, close set—the corners of a regular tetrahedron? So beautiful…. But what was the range? Was this some kind of ball lightning, just a few hundred yards above the field?
In another few minutes they would be too faint to see. But there were other lights now, bright flashes beyond the eastern ridgeline. In the west, pinpricks of light slid faster and faster toward the zenith. A shimmering veil of light spread behind them.
